1. Field of the Invention
The present invention relates to image forming equipment and, in particular, to image forming equipment such as a printer, a copying machine, a facsimile machine, and the like which use toners to form an image onto recording paper according to an electrophotographic method. The present invention further relates to a technique for detecting the residual quantity of the toners.
2. Description of the Related Art
The present inventors have developed image forming equipment which includes: a developing device which supplies toners to the surface of a photosensitive member and develops a latent image on the surface of the sensitive member to thereby form a toner image; a cleaning device which, after the toner image formed by the developing device is transferred to paper, removes and collects the residual toners attached to the surface of the sensitive member; a toner delivery device, interposed in a closed loop between the developing device and the cleaning device, which delivers a portion of the surplus toners that have not been used for development in the developing device to the cleaning device and delivers the residual toner collected by the cleaning device to the developing device; and toner supply means, which supplies the toners to a toner delivery path of the toner delivery device.
In such image forming equipment, the delivery of the toners is entrusted to the toner delivery device and the toners is supplied to the toner delivery path R, which makes it possible to miniaturize not only the developing device but also the whole image forming equipment and, at the same time, to improve the degree of freedom of the layout to a great extent. Now, in Japanese Patent Publication No. 63-246780 of Showa, there is disclosed image forming equipment which includes: a belt-shaped member interposed between the interior of a developing device as described above and the interior of a cleaning device, which removes and collects the residual toners attached to the surface of the photosensitive drum, the belt-shaped member being driven around the cleaning and developing devices; and toner removing means, provided in the developing device, for removing the residual toners attached to the surface of the belt-shaped member in the interior of the cleaning device from the belt-shaped member in the interior of the developing device. However, the belt-shaped member disclosed in the image forming equipment does not deliver part of the surplus toners that have not been used for development in the developing device to the cleaning device. Also, in the subject publication (that is, Japanese Patent Publication No. 63-246780 of Showa), no teaching is disclosed regarding a toner supply means which is used to supply toners to the toner delivery path of the toner delivery device.
On the other hand, in the image forming equipment which uses toners to form an image on recording paper according to an electrophotographic method, it is necessary to provide a toner residual quantity detection device which detects the residual quantity of the toners because recording is impossible if the toners run out in the developing device.
In conventional image forming equipment, normally, for example, as disclosed in Japanese Patent Publication No. 4-97179 of Heisei, the toner residual quantity detection device is provided in the developing device.
However, when the toner residual quantity detection device is provided in the developing device as in the conventional image forming equipment, the developing device becomes inconveniently large.
Therefore, if this conventional technique is used in the image forming equipment developed by the present inventors, the resulting combination goes against the object of the image forming equipment (i.e., the miniaturization of the developing device) and is thus not desirable.